1. Field of the Invention
The present invention relates to a slider assembly that prevents a slider from coming off rail members, such as track rails, dummy track rails or insertion sleeves, during the transport and assembly of the slider for use in a linear-motion rolling guide unit applied to linear sliding portions of such equipment as machine tools, assembling apparatuses, test equipment.
2. Description of the Prior Art
Advances of mechatronics technology have been remarkable in recent years and the fundamental and versatile equipment supporting such a technology include linear-motion rolling guide units. The linear-motion rolling guide units are currently used by being incorporated in equipment of various fields including machine tools, semiconductor fabrication equipment, transport equipment and industrial robots. The linear-motion rolling guide units are finding an ever widening range of applications as the technology advances and there are growing demands for an easy-to-handle linear-motion rolling guide units.
A conventional linear-motion rolling guide unit as shown in FIG. 10 has first raceway grooves 24 formed on longitudinal sidewall surfaces 23, 23, thereof on both sides of a track rail 22. A slider 21 is mounted astride the track rail 22 and freely slides on the track rail 22 with rolling elements 27 circulating along the first raceway grooves 24. The track rail 22 is formed in its longitudinal upper surface 34 with mounting holes 33 spaced from each other. The slider 21 has a casing 25 movable relative to the track rail 22 and end caps 26 mounted to the longitudinal ends of the casing 25. The casing 25 has return passages 31 formed therein in which the rolling elements 27 roll and circulate. The casing 25 is formed in its upper surface with threaded holes 39 for mounting other devices and components. The casing 25 and the end caps 26 are formed at their undersides with recessed portions 30 so that the casing 25 and the end caps 26 can move astride the track rail 22. The recessed portions 30 are formed with raceway grooves 29 at positions opposing the first raceway grooves 24 of the track rail 22. The raceways formed by the opposing raceway grooves 24 and 29 accommodate the rolling elements 27 such as balls and cylindrical rollers so that they can move rolling in the raceways. To prevent the rolling elements 27 from coming off the casing 25, the casing 25 has retainer bands 38 enclosing the rolling elements 27. Bolts are inserted through the mounting holes 33 formed in the longitudinal upper surface 34 of the track rail 22 and screwed into threaded holes formed in a mounting body (not shown), such as bed, bench and machining table, to securely mount the track rail 22 on the mounting body.
The end caps 26 have formed on both sides thereof with claws to scoop the rolling elements 27 from the first raceway grooves 24--the loaded raceways that face the track rail 22--and direction change passages to change the direction of travel of the rolling elements 27 for circulation. The end caps 26 have end seals 37 attached thereto that seal between the track rail 22 and the longitudinal ends of the slider 21, and grease nipples 40 for supplying a lubricant to the raceways formed by the raceway grooves 24 and 29 of the track rail 22 and slider 21. The end caps 26 are secured to the longitudinal ends of the casing 25 by screws 42 inserted through mounting holes. The rolling elements 27 running loaded along the raceway grooves 24 of the track rail 22 are led into the direction change passages formed in the end caps 26, and then move into the return passages 31 formed parallel to the raceway grooves 29 of the casing 25. Thus the rolling elements 27 continuously travel in endless circulation passages. The rolling motion of the rolling elements 27 loaded between the raceway grooves 24 formed in the track rail 22 and the raceway grooves 29 formed in the slider 21 allows a smooth relative motion between the track rail 22 and the slider 21.
The conventional linear-motion rolling guide unit has been marketed with the slider 21 mounted astride the track rail 22 or in a preset condition, as shown in FIG. 10. In the actual operation, too, a combined set of the slider 21 and the track rail 22 has been in use. As demands for the linear-motion rolling guide unit have expanded progressively, they have also diversified and come to include interchangeability as a means for facilitating handling. Because of a high level of precision management established for manufacturing and assembly, it has been possible these days to combine an arbitrary track rail with an arbitrary slider, provided they are compatible with each other in the engagement specification. Under these circumstances, the track rails and the sliders are separately sold to meet the needs for replacing only the slider while using the existing track rail, or vice versa.
During their storage, sale and assembly, the interchangeable sliders are not handled alone but are combined, as a set, with track rail-shaped rail members inserted into the sliders for the protection and prevention of the rolling elements in the sliders from getting dislocated. When a small number of interchangeable sliders are handled, it is possible to use the rail members or dummy track rails that have the same materials and specifications as the real track rails on which the interchangeable sliders are to be mounted. When a large number of interchangeable sliders are handled, however, insertion sleeves instead of the dummy track rails are used which are molded from resin or the like in shapes resembling the dummy track rails because manufacturing the dummy track rails will raise cost. An insertion sleeve 52 is an elongate body of an appropriate length having a hollow portion 53 therein as shown in a cross section of FIG. 13. The insertion sleeve 52 has escape grooves 55 formed in longitudinal sidewall surfaces 54 on both sides. The escape grooves 55 do not need to sustain the loads acting on the linear guide unit but have upper and lower rolling contact portions 56 arc-shaped in cross section that are in contact with rolling elements 57 shown by imaginary lines. The areas between the upper and lower rolling contact portions 56 form the escape grooves 55 accommodating the retainer bands 38 and constituting non-contact portions.
The user who purchased the set of the slider 21 mounted on the insertion sleeve 52, as shown in FIG. 12, puts the insertion sleeve 52 against the end of the real track rail 22 on which to fit the slider 21 and slides the slider 21 from the insertion sleeve 52 onto the track rail 22. This allows the slider 21 to be moved from the insertion sleeve 52 to the track rail 22 without the rolling elements 57 falling from the slider 21.
Small linear-motion rolling guide units do not have ball retaining means such as retainer bands 38 and thus pulling the slider from the track rail results in balls or rolling elements contained in the slider falling out of the slider. To avoid this, it is proposed to use a dislocation prevention device with some strength in the track rail. Conventional dislocation prevention devices for the linear guide units include, for example, a stopper device shown in FIG. 11, which comprises rubber stoppers 45 fitted in the mounting holes 33 that are formed at the ends of the track rail 22 in the linear-motion rolling guide unit shown in FIG. 10 and through which the track rail mounting bolts are to be inserted. When the slider 21 is about to move beyond the track rail 22, the slider 21 physically abuts against the rubber stoppers 45 and stops. In a track rail too short for the mounting holes 33 to be formed at the ends of the track rail 22, it is conventional practice to fit rubber O-rings (not shown) at the ends of the track rail 22 to work as the stoppers.
A stopper device for the linear guide unit disclosed in Japanese Patent Laid-Open No. 4640/1997 comprises: notches crossing widthwise the upper or lower surface of the guide rail at the end portions of the guide rail, which has rolling element grooves axially extending on a pair of longitudinal sidewall surfaces thereof; and engagement members fitted in the notches and at least partly projecting from the outer surface of the guide rail to engage the slider. The engagement members are inserted into the notches of the guide rail for a single operation mounting. Because the slider abuts against the stopper device, the slider is prevented from overrunning and coming off the ends of the guide rail. The stopper device may be made of a steel wire or steel plate or a plate member of synthetic resin.
A linear-motion rolling guide unit disclosed in the Japanese Utility Laid-Open No. 27337/1993 has stoppers that are mounted to or dismounted from the track rail by vertical pushing or pulling. The stoppers are so shaped that the distance between their locking legs at the ends of a stopper body is set smaller than the distance between the raceway grooves for the rolling elements formed at both sidewall surfaces of the track rail. When the locking legs are fitted between the raceway grooves, an elastic deformation of the stopper body brings a part of its inner surface into elastic contact with a part of the top surface of the track rail. The stopper is fitted by vertically pushing it onto the track rail and removed by vertically pulling it off. The engagement of the locking legs is achieved by using bolt holes and recessed grooves or the like formed in the top surface of the track rail.
The above dislocation prevention device for the linear-motion rolling guide unit has its locking portions bent and given a certain strength so that the dislocation prevention device can work as a stopper even when the slider strikes it at significantly high speeds. Hence, the dislocation prevention device has drawbacks that attaching and removing the stoppers requires a force and that it has been difficult to reduce manufacture cost. Further, the conventional stoppers require forming notches at the end portions of the guide rail and are fixedly secured to the notches and the raceway grooves. Therefore, if such stoppers are applied as it is to a longitudinally intermediate part of the guide rail, the notches will reduce the strength of the guide rail and can score the raceway grooves when the stoppers are attached to or removed from the raceway grooves or while held in the raceway grooves. In the dislocation prevention devices in which rubber stoppers are fitted in the mounting holes formed at the end portions of the track rail through which the mounting bolts are to be inserted, or in which rubber O-rings are attached to the ends of the track rail, the rubber stoppers and O-rings may get dislocated from the mounting holes or track rails by impacts. Increasing the press fit with which the rubber stoppers are fitted into the mounting holes or using O-rings with greater strengths to prevent the stopper devices from coming off the track rail will make the mounting of the rubber stoppers and the rubber rings to the mounting holes and track rail difficult. Further, the conventional stoppers need to be installed on both sides of the slider with respect to the sliding direction. Under these circumstances, there are growing demands for a slider assembly which, as the dislocation prevention device for preventing the slider from coming off the rail member, uses stoppers having a simpler structure, easy to be attached and removed and less costly to manufacture, and which can be reliably held in the track rail to work as a stopper even when the track rail is short.